I've used some SRAM components but not enough to offer feedback.

I have experience with both Shimano and Campy and I've gotten better performance from Shimano. My Campy is tempermental-needs more attention that I gave the Shimano. Not sure how much truth there is to it, but it sounds like Shimano has not worked out all the kinks with the 7900 Dura Ace stuff. Some folks are not satisfied with the shifting quality while others are okay. I've had really good luck with the Dura Ace 7800/7801 10 sp (older 10 sp version) and you could probably put together a great setup using that modle and at a lot lower cost than the newer 7900. The major difference is you still have the exposed cable housings on the 7800 versus the cleaner looking 7900. I would highly recommend the 7800 53/39 crank or the R700 (or latest version) 50/34 crank. Outstanding components.